The number of heavy commercial trucks on American highways is increasing every year. As the number of heavy commercial trucks increases, the types of people who drive these trucks is changing. Many of the new drivers are women who find the effort required to operate a manual clutch on a heavy commercial truck physically difficult.
The pedal force required to operate a manual clutch on a heavy commercial truck can be as high as 75 pounds. This pedal force is approximately twice the force required to operate a manual clutch on a light vehicle. Frequent shifting in high density traffic or holding the clutch pedal down during long stops can be fatiguing. Power assistance to reduce the effort required to operate the manual clutch of a heavy commercial truck is thus desirable.
The concept of providing power assistance for manually operated devices is not new. There are many existing techniques to accomplish power assistance. These devices tend to be complicated which makes them expensive and comprises reliability. Also, these devices frequently have slow response time and they do not provide assistance proportional to the pedal effort.
To provide power assistance for reducing the effort to operate a manual clutch, it is desirable to have a device that provides assistance that is proportional to the effort exerted on the clutch pedal, thereby maintaining the "natural feel" of the operation of the clutch. The response of the device should be quick enough to allow the driver to double clutch when shifting the transmission and the device should be relatively simple to keep manufacturing costs low and reliability high.
Although much of the discussion herein relates to the application of power assistance devices which reduce the effort of operating manual clutches on heavy commercial trucks, it is not intended that the invention be limited to such operations. It will be obvious from the description that follows that the present invention will be useful in other vehicles facing the problems common to those described herein.